Lemma 2.3 ([1]}) 
Let \(\Omega \)  be an open set in \({\mathbb {R}}^N\)  and \(u\in W^{2,q}_{\text{loc}}(\Omega )\cap L^q(\Omega )\) , \(1<q<\infty \) , be a strong solution of
\(-\operatorname{tr}\left(A(x) D^2 u\right) = g\qquad \text{in }\Omega ,\) 
